Variable capacity circuit and control method of variable capacity circuit

Abstract

To present a variable capacity circuit and a control method of variable capacity capable of extending a variable capacity width of a variable capacity element to a maximum extent without increasing an element area of the variable capacity element or varying the level of control voltage, a variable capacity circuitcomprises a capacity value control circuitvaractors VAand VAand resistance elements Rand RThe capacity value control circuitissues a variable output voltage CNTOUT depending on input control voltage VT, and controls the potentials at both ends of the varactors simultaneously. The output voltage CNTOUT is variably adjusted so as to have a negative correlation to the control voltage VT. Variable width of terminal voltage VD can be extended from a variable width SAto a variable width SA(range is +/−(Vcc)). As a result, as shown in, the changeable area of a varactor capacity value CV can be extended from a changeable area CAto a changeable area CA